A detailed examination of a well-preserved Archaeopteryx fossil housed at Chicago’s Field Museum has unveiled new insights into the biology of this pivotal Jurassic-era creature. Known as one of the earliest and most famous examples of the bird-dinosaur transition, Archaeopteryx lived around 150 million years ago and continues to shape our understanding of avian evolution.
The fossil, originally found in southern Germany, is considered one of the most complete of the 14 known Archaeopteryx specimens discovered since 1861. The original discovery supported Charles Darwin’s theory of evolution by revealing a blend of reptilian and bird-like features, affirming that modern birds descended from dinosaurs.
Using ultraviolet light and CT scanning, scientists were able to identify previously hidden details in the fossil’s feathers, limbs, and skull. These advanced imaging techniques revealed structures not visible through traditional examination, such as soft tissues and delicate bones still encased in rock.
Notably, researchers detected specialized feathers known as tertials—the innermost flight feathers attached to the humerus—on both wings. These feathers, now common in modern birds but previously unseen in feathered dinosaurs, suggest that this feature may have evolved specifically to support flight.
“For wings to generate lift, the aerodynamic surface needs to be continuous with the body,” explained lead researcher Jingmai O’Connor, a paleontologist at the Field Museum. “The discovery of tertials in Archaeopteryx shows how these dinosaurs began closing that gap.”
While Archaeopteryx was capable of flight, the fossil also indicates it likely spent significant time on the ground. The preserved soft tissue in the toe pads and the structure of the feet suggest a terrestrial lifestyle, though the animal still retained climbing capabilities. The mobility of its first and third fingers may have helped it navigate trees.
The study also provided a clearer view of its skull. Unlike most modern birds, Archaeopteryx had an immobile skull, but its skeletal structure hints at the early development of cranial kinesis—a trait that allows modern birds to move their beaks independently from their skulls.
For the first time, researchers documented the full length of the animal’s vertebral column, counting 24 vertebrae—one more than previously recorded. This adds another layer to the growing understanding of its anatomy.
This particular fossil, which had been in private collections since the 1990s, was acquired by the Field Museum in 2024. Its exceptional three-dimensional preservation allowed scientists to examine it in greater detail than many previous specimens, which were flattened over time.
“This is likely the best Archaeopteryx specimen ever found,” O’Connor noted. “It continues to inform us not only about bird origins but also about evolutionary biology as a whole.”
Calling Archaeopteryx “the icon of evolution,” O’Connor emphasized its unique role in bridging the evolutionary gap between dinosaurs and modern birds—one of the most successful groups of vertebrates alive today.
